Reproductive, developmental, and neurobehavioral effects of methylmercury in fishes

In the decades since the Minamata tragedy in Japan, there has been a considerable body of research performed on effects of methylmercury in fishes. The studies have revealed that some of the most sensitive responses seen in fishes are reminiscent of the symptoms experienced by the Minamata victims. This article reviews the literature, with a focus on mercury's effects on fish reproduction (hormone levels, gametogenesis, fertilization success), embryonic development (morphological abnormalities, rate), the development of behavior, and neurobehavioral effects in adults. Both experimental exposures and epidemiological approaches are included. There have been many studies demonstrating delayed effects of mercury exposure in that exposures during one life history stage can produce effects much later during different life history stages. For example, exposure of maturing gametes can result in abnormal embryos, even though the embryos were not themselves exposed to the toxicant. Exposures during sensitive embryonic periods can produce long-lasting effects that can be seen in adult stages. The existence of these manifold delayed effects renders the practice of short-term toxicity testing particularly unhelpful for understanding the effects of this (and other) toxicants.